Spark ignition apparatus for internal combustion engines



y 7, 1964 N. A. JUKES 3,139,876

SPARK IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Filed July 26. 1961 3 Sheets-Sheet 1 N. A. JUKES July 7, 1964 SPARK IGNITICN APPARATUS FOR INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet 2 Filed July 26. 1961 Fig.5

43 70 ENG/MEAN? INLET July 7, 1964 JUKES 3,139,876

SPARK IGNITICN APPARATUS FOR INTERNAL COMBUSTION ENGINES Filed July 26. 1961 3 Sheets-Sheet 5 United States Patent 3,139,876 SPARK IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Norman Alfred Jukes, Walsall, England, assrgnor to Joseph Lucas (Industries) Limited, Brrmmgham, England Filed July 2'6, 1961, Ser. No. 127,034 Claims priority, application Great Britain Aug. 16, 1960 6 Claims. (Cl. 123-148) The object of this invention is to provide a spark ignition apparatus for an internal combustion engine in a convenient form whereby the need for a conventional interrupter is obviated.

Spark ignition apparatus according to the invent on comprises a generator driven by the engine for producing a voltage which varies periodically within limits determined by the speed of the engine, a trigger circuit operable by the generator output and arranged to produce an output pulse at a predetermined voltage during each voltage cycle of the generator, and a control circuit operable by said output pulse for supplying a sparking voltage to a sparking plug of the engine.

In the accompanying drawings:

FIGURE 1 is a front view of the rotor employed in a generator in accordance with one example of the invention;

FIGURE 2 is a sectional side view of the rotor;

FIGURE 3 is a sectional side view of the associated stator;

FIGURE 4 is a front view illustrating the relationship between the stator and rotor;

FIGURE 5 is a circuit diagram illustrating one example of the trigger and control circuits, and

FIGURE 6 illustrates a further trigger and control circuit.

The generator illustrated in FIGURES 1 to 4 is suitable for use with a four cylinder engine, and includes a stator 11 (FIGURES 3 and 4) incorporating two permanent magnets 12 and three pole pieces 13, 14, 15 separated by a resin moulding 16. Embedded within the moulding 16 are a pair of pick-up coils 17, 18 which surround the poles 13, 15 respectively. The stator 11 is fixed to the body of the engine, whilst the rotor 19 is fixed to the engine crankshaft for rotation therewith. The rotor 19 is of generally annular form, but at diametrically opposite positions has secured thereto a pair of magnetic plates 20 which rotate between the extremities of the poles 13, 14 as shown in FIGURE 4. The plates 20 when considered in the direction of rotation of the rotor 19 vary from a minimum radial width to a maximum radial width at the points 21. It will be appreciated that the voltage generated in the coil 17 will depend on the speed of rotation of the rotor and on the radial thickness of the portion of a plate 20 between the poles 13, 14. Thus, during each half-revolution of the crankshaft the voltage developed in the coil 17 will vary between limits determined by the speed of rotation and the shape of the plates 20, so that by suitably shaping the latter any desired relationship between the speed of rotation and the voltage output of the generator can be obtained.

The generator produces a secondary output in the coil 18 by virtue of a pair of studs 22 passing between the poles 14, 15. The studs are conveniently of square crosssection, but may be of any other cross-section such that the leading edge of each stud cuts the lines of force at right angles when passing between the poles 14, 15. The positioning of the studs 22 is such that a relatively large voltage will be developed in the coil 18 immediately before the maximum voltage is developed in the coil 17.

The purpose of this additional coil will be described later.

The generator output (i.e. the output from the coil 17) is fed to a trigger circuit which produces an output pulse each time the generator output reaches a predetermined voltage. Further, this output pulse is used to trigger a control circuit which controls the supply of power to the sparking plugs of the engine. It will be understood that for a given shape of the rotor the trigger circuit will produce an output pulse at a point determined by the angular velocity of the crankshaft, and hence an automatic advance mechanism is provided in accordance with a law determined by the shape of the plates 20.

Referring now to the example of a trigger and control circuit shown in FIGURE 5, there is provided a pair of supply terminals 23, 24 adapted for connection respectively to the positive and negative terminals of a 12-vo1t battery or other convenient source of direct or rectified alternating current. The terminal 23, which may be grounded, is connected through a resistor 25 to the base terminal of a transistor 26 of the p-n-p type. The emitter terminal of this transistor is connected to the terminal 23, through a resistor 27. Further, the collector terminal of the transistor 26 is connected to the terminal 24 through the primary winding 28 of a transformer 29, further resistors 30, 31 and a switch 32, the winding 28 being bridged by parallel circuits containing respectively a resistor 33 and a diode rectifier 34, and a capacitor 46. A point intermediate the resistors 30, 31 is connected to the terminal 23 through a Zener diode 35.

The base terminal of the transistor 26 is further connected through a diode rectifier 36 to the collector terminal of a second p-n-p type transistor 37. The emitter terminal of the transistor 37 is connected to the terminal 23 through the resistor 27, whilst its collector terminal is connected to the resistor 31 through a thermistor 38 and a resistor 39, the thermistor being bridged by a resistor 40.

v The base terminal of the transistor 37 is connected through a resistor 41 to the slider of a variable resistor 42, the slider being movable by pressure-sensitive means 43 responsive to the pressure in the air inlet of the engine. The pressure sensitive means includes a diaphragm 43a connected to the slider of the variable resistor 42 and subjected to the pressure in the air inlet of the engine, this pressure acting to move the diaphragm against the action of a spring 43b. The slider of the resistor 42 is connected through a diode rectifier 44 and a resistor 45 in parallel to the terminal 23, whilst the resistor 42 is connected to the terminal 23 through the coil 17. Furthermore, a capacitor 47 is connected across the resistor 41, and the base terminal of the transistor 37 is connected through the capacitor 47 and a diode rectifier 48 to one end of the coil 18, the other end of which is connected to the terminal 23.

The control circuit includes an ignition coil 50 having a primary winding 51, a secondary winding 52 adapted for connection to the spark plugs of the engine, and a control winding 53. The winding 51 is bridged by a diode rectifier 54 and has one end connected to the terminal 24 and its other end connected to the collector terminal of a p-n-p type transistor 55. The base terminal of the transistor 55 is connected through the winding 53 to one end of the secondary winding 56 of the transformer 29, the other end of the winding 56 being connected to the emitter terminal of the transistor 55 and to theterminal 23.

Discounting momentarily the effect of the means 43 and the coil 18, the operation of the circuit is as follows:

When the voltage across the generator winding 17 is below a predetermined value, the transistor 26 is conductive and the resultant voltage across the resistor 27 ensures that the transistor 37 is non-conductive. Current flows through the transistor 26 to the winding 28 but this current is constant and hence no output is generated in the winding 56. When the output voltage of the generator winding 17 reaches said predetermined voltage, the transistor 37 is rendered conductive by virtue of the voltage applied to its base terminal through the coil 17, the resistor 42, and the resistor 41. When the transistor 37 conducts the bias on the base of the transistor 26 is reduced. This reduces the current flow through the transistor 26 causing a reduction in the voltage across the resistor 27 and hence permitting a larger flow through the transistor 37. This regenerative action continues until the transistor 26 is non-conductive, and during the regenerative action the current in the primary winding 28 of the transformer 29 drops sharply to induce an output pulse in the winding 56.

The transistor 55 in the control circuit is normally nonconductive. However, when an output pulse is received by the winding 56 from the triggering circuit, the base of the transistor 55 is biased to render it conductive and allow a current to fiow to the primary winding 51. This current in turn induces a voltage in the control winding 53, which biases the transistor 55 further. This regenerative action continues until the core 50 is saturated. At this point no further energy is fed back to the transistor 55, which becomes non-conductive. The rapid rise of current in the primary winding 51 induces a high voltage in the secondary winding 52, whilst the back in the primary winding when the current falls as a result of saturation of the core 50 is conducted through the rectifier 54 inter-connecting its ends. Successive high voltages induced in the secondary winding 52 are fed through a distributor 57 to the engine spark plugs 58 in turn.

When the voltage across the winding 17 falls the trigger circuit reverts to its initial condition, whereafter the cycle can be repeated.

As previously explained the circuit described provides an automatic advance of timing with engine speed by virtue of the fact that the output voltage of the generator is proportional to speed, so that the instant in each voltage cycle of the generator at which the trigger circuit produces an output pulse is also dependent on speed. The purpose of the means 43 is to give automatic advance or retard of timing in response to the pressure in the air inlet of the engine by varying the proportion of the voltage across the coil 17 which is fed to the base terminal of the transistor 37.

The purpose of the coil 18 is to overcome a disadvantage which may occur at low speeds, in that the spark is difiicult to obtain or occurs at irregular intervals. The coil 18 receives a relatively large voltage pulse once during each half-cycle and this pulse operates the trigger circuit if a pulse from the coil 17 has not already done so. The purpose of the rectifier 48 is to prevent the coil 18 from shunting the coil 17.

A further example of a combined trigger and control circuit is illustrated in FIGURE 6, in which there are provided terminals 111, 112 adapted for connection to the negative and positive terminals of a 12 volt battery or other convenient source of direct or rectified alternating current. The circuit further includes a square-loop ferrite or other square-loop core 113 having thereon three windings 114, 115, 116 and an ignition coil 117 having a primary winding 118 and a secondary winding 119, one end of each winding 118, 119 being connected through a resistor 120 to a terminal 111a of a high voltage supply, and the winding 119 being adapted for connection to the spark plugs of the engine.

The other end of the winding 118 is connected to one end of the winding 114, and through the cathode and anode of a control rectifier 121, to the terminal 112. Further, the other end of the winding 114 is connected to the gate terminal of the control rectifier 121, and the winding 118 and rectifier 121 are bridged by a capacitor 112.

One end of the winding 116 is connected to the terminal 111, whilst its opposite end is connected the terminal 111 through a diode rectifier 123 and, through a resistor 124, to the collector terminal of a transistor 125. The emitter terminal of the transistor 125 is connected to the terminal 111 through a resistor 126, and to the terminal 112 through a resistor 127 and a capacitor 128 in parallel. The base terminal of the transistor 125 is connected to the terminal 112 through a diode rectifier 129, and is also connected to one end of the winding 115, the other end of which is connected to the terminal 112 through a coil 130 Wound on the generator stator.

In operation, the transistor 125 and the control rectifier 121 are normally non-conductive and the capacitor 122 becomes charged through the resistor 120. When a signal is received by the coil 130, the transistor 125 commences to conduct, thereby permitting current flow through the winding 116. The resultant induced current in the winding 115 permits further conduction of the transistor, and thus a regenerative action is initiated and continues until the core 113 changes state. At this point a large signal appears in the winding 114 and renders the control rectifier 121 conductive. The capacitor 122 now discharges through the winding 118, inducing a high voltage in the winding 119. When the capacitor is discharged, the back in the winding 118 cuts off the control rectifier 121. The core 113 is switched to its original state by a reverse signal appearing in the coil 130 this signal being conducted through the rectifier 129.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. Spark ignition apparatus for an internal combustion engine, comprising in combination a generator having a stator, a rotor driven by the engine, an output coil, and means associated with the stator and rotor for generating across said output coil a voltage which during each revolution of the engine varies from a minimum to a maximum a number of times dependent on the number of engine cylinders, a trigger circuit operable by the voltage across said output coil to produce an output pulse when the voltage across said output coil reaches a predetermined value, a control circuit operable by said output pulse for supplying a sparking voltage to a spark plug of the engine, a second output coil forming a part of the generator, means associated with said stator and rotor for generating a voltage in said second coil at an instant in each voltage cycle before the maximum output voltage is attained across the first-mentioned output coil, the second output coil being associated with the trigger circuit so that in each voltage cycle the voltage generated in said second coil will operate the trigger circuit in the trigger circuit has not previously been operated by the voltage across the first-mentioned output coil.

2. Spark ignition apparatus as claimed in claim 1 including a variable resistor for determining the predetermined voltage at which the trigger circuit will be operated, and means operable by the pressure in the air inlet of the engine for determining the setting of the variable resistor.

3. Spark ignition apparatus as claimed in claim 1 in which the trigger circuit is a bistable multivibrator including a pair of transistors having a common emitter resistor for ensuring rapid switching of the multivibrator.

4. Spark ignition apparatus as claimed in claim 1 in which the trigger circuit includes a square loop core which is driven by the generator output from one stable state to its other stable state to produce said output pulse.

5. Spark ignition apparatus as claimed in claim 1 in which the control circuit includes an ignition coil having a secondary winding connectible to the engine spark plugs in turn, a primary winding, and a transistor operable by said output pulse to control current flow in the primary winding.

5 6 6. Spark ignition apparatus as claimed in claim 1 in References Cited in the file of this patent which the control circuit includes an ignition coil having a secondary winding connectible to the engine spark plugs UNITED STATES PATENTS in turn, a primary winding, and a control rectifier oper- 2852588 Hartman Sept 19587 able by said output pulse to control current flow in the 5 2,898,392 Jaeschke 1959 primary winding. 2,953,719 Guiot Sept. 20, 1960 

1. SPARK IGNITION APPARATUS FOR AN INTERNAL COMBUSTION ENGINE, COMPRISING IN COMBINATION A GENERATOR HAVING A STATOR, A ROTOR DRIVEN BY THE ENGINE, AN OUTPUT COIL, AND MEANS ASSOCIATED WITH THE STATOR AND ROTOR FOR GENERATING ACROSS SAID OUTPUT COIL A VOLTAGE WHICH DURING EACH REVOLUTION OF THE ENGINE VARIES FROM A MINIMUM TO A MAXIMUM A NUMBER OF TIMES DEPENDENT ON THE NUMBER OF ENGINE CYLINDERS, A TRIGGER CIRCUIT OPERABLE BY THE VOLTAGE ACROSS SAID OUTPUT COIL TO PRODUCE AN OUTPUT PULSE WHEN THE VOLTAGE ACROSS SAID OUTPUT COIL REACHES A PREDETERMINED VALUE, A CONTROL CIRCUIT OPERABLE BY SAID OUTPUT PULSE FOR SUPPLYING A SPARKING VOLTAGE TO A SPARK PLUG OF THE ENGINE, A SECOND OUTPUT COIL FORMING A PART OF THE GENERATOR, MEANS ASSOCIATED WITH SAID STATOR AND ROTOR FOR GENERATING A VOLTAGE IN SAID SECOND COIL AT AN INSTANT IN EACH VOLTAGE CYCLE BEFORE THE MAXIMUM OUTPUT VOLTAGE IS ATTAINED ACROSS THE FIRST-MENTIONED OUTPUT COIL, THE SECOND OUTPUT COIL BEING ASSOCIATED WITH THE TRIGGER CIRCUIT SO THAT IN EACH VOLTAGE CYCLE THE VOLTAGE GENERATED IN SAID SECOND COIL WILL OPERATE THE TRIGGER CIRCUIT IN THE TRIGGER CIRCUIT HAS NOT PREVIOUSLY BEEN OPERATED BY THE VOLTAGE ACROSS THE FIRST-MENTIONED OUTPUT COIL. 